A. Field of the Invention
The present invention relates generally to methods and nucleic acid sequences useful as probes for the identification of a region within human chromosome 8q24. The invention also relates to diagnostic techniques for the detection of particular forms of human cancer. More particularly, it concerns probes and methods useful in monitoring the progression of prostate cancer through the use of fluorescence in situ hybridization techniques.
B. Description of the Related Art
Carcinoma of the prostate (PCA) is the second-most frequent cause of death in men in the United States (Boring, 1994). The increased incidence of prostate cancer during the last decade has established prostate cancer as the most prevalent of all cancers (Carter and Coffey, 1990). Although prostate cancer is the most common cancer found in United States men, (approximately 200,000 newly diagnosed cases/year), the molecular changes underlying its genesis and progression remain poorly understood (Boring et al., 1993). According to American Cancer Society estimates, the number of deaths from PCA is increasing in excess of 8% annually.
Unfortunately, due to the extreme variability in the natural history of this disease, coupled to frequent incidental diagnosis of subclinical disease (following prostate-specific antigen [PSA] testing or transurethral resection for urinary obstruction) no genetic markers have been identified which could discriminate prostate cancers likely to progress to lethal metastatic disease (Ruckle et al., 1993).
Furthermore, the ability to accurately assay the metastatic spread of an individual tumor of the prostate is also not available. Genetic alterations have not been identified that could serve as prognostic markers relevant to clinical decision-making. Although clinical and pathologic stage and histological grading systems (e.g., Gleason's) have been used to indicate prognosis for groups of patients based on the degree of tumor differentiation or the type of glandular pattern (Carter and Coffey, 1989; Diamond et al., 1982), these systems do not predict the progression rate of the cancer. While the use of computer-system image analysis of histologic sections of primary lesions for "nuclear roundness" has been suggested as an aide in the management of individual patients (Diamond et al., 1982), this method is of limited use in studying the progression of the disease.
The analysis of DNA content/ploidy using flow cytometry, and fluorescence in situ hybridization (FISH) have recently been demonstrated to have utility as a marker of prostate cancer aggressiveness (Pearsons et al., 1993; Macoska et al., 1994; Visakorpi et al., 1994; Takahashi et al., 1994; Alcaraz et al., 1994; Pearsons et al., 1993), but these methods are expensive, time-consuming, and the latter methodology requires the construction of centromere-specific probes for analysis. Finally, despite the use of comparative genomic hybridization (CGH) in prostate cancer specimens, characteristics that distinguish aggressive versus indolent PCA remain unclear.
The inability to identify patients who are more likely to progress or do poorly despite therapy causes both uncertainty and disappointment in clinical management of patients with such cancer.
In human breast cancer, the presence of particular gene(s) has been linked to indication of disease progression. One such example is the detection of a human breast cancer gene on chromosome 17 (17q21) (Miki, et al. 1994; Futreal et al. (1994). Unfortunately, no study has identified similar important genes in prostate cancer. Although extrachromosomal dmins have been reported in some prostate tumor specimens (Brothman et al., 1990; Lundgren et al., 1992; Milasin et al., 1994), no evidence of chromosomal gene amplification of known oncogenes has yet been reported.
Recent studies have identified several recurring genetic changes in prostate cancer including: 1) allelic loss (particularly loss of chromosome 8p and 16q) (Bova, et al., 1993; Macoska et al., 1994; Carter et al., 1990); 2) generalized DNA hypermethylation (Isaacs et al., 1994); 3) point mutations or deletions of the retinoblastoma (Rb) and p53 genes (Bookstein et al., 1990a; Bookstein et al., 1990b; Isaacs et al., 1991); 4) alterations in the level of certain cell-cell adhesion molecules (i.e., E-cadherin/alpha-catenin) (Carter et al., 1990; Morton et al., 1993; Umbas et al., 1992) and aneuploidy and aneusomy of chromosomes detected by FISH, particularly chromosomes 7 and 8(Macoska et al., 1994; Visakorpi et al., 1994; Takahashi et al., 1994; Alcaraz et al., 1994). It seems certain, that a combination of these changes is critical to the acquisition of metastatic potential, and Isaacs and colleagues (Isaacs et al., 1994) have recently proposed a model placing these genetic changes in the context of prostate cancer disease progression.
One approach to the analysis of amplified DNA sequences has relied on DNA electrophoresis (e.g., in gel renaturation or restriction landmark genomic scanning). While these techniques successfully identify amplified sequences, they are extremely laborious and can be confounded by amplified sequences unrelated to the phenotype of interest.
These and other inherent deficiencies in the prior art evidences the tremendous need in the medical arts not only for the identification of the gene linked with the progression of prostate cancer, but also the need for a diagnostic method to monitor this progression. Likewise, the identification of a commonly amplified chromosome region in prostate cancer would be of considerable importance, and the development of a rapid, inexpensive method to detect such amplification would provide a significant contribution to the area of cancer diagnosis, monitoring, and treatment.